Insulation panel for construction and manufacturing method thereof

ABSTRACT

The invention relates to a multilayer thermal insulation panel for construction ( 100 ) and manufacturing method thereof. Such panel comprises: —a main layer ( 1 ) in thermally insulating material which comprises a first surface ( 10 ) and a second surface ( 20 ); —a first backing layer ( 2 ) of the main layer connected to the main layer along the first surface ( 10 ); a second backing layer ( 5 ) of the main layer connected to the main layer along the second surface ( 20 ). At least one of such first ( 2 ) and second ( 5 ) backing layers comprises: —a reinforcement layer ( 3 ) in fibrous material, a fire-resistant ( 4 ) and thermally insulating layer, —a cladding layer ( 6 ) of the reinforcement layer ( 3 ); —a binding layer ( 7 ) positioned on a surface ( 8 ) of the fire-resistant layer ( 4 ) in such a way that the fire-resistant layer is sandwiched between the cladding layer ( 6 ) and the binding layer. The panel is characterised in that the binding layer ( 7 ) is manufactured by means of. a spray-applied aqueous solution of sodium silicates on the surface ( 8 ) of the fire-resistant layer ( 4 ).

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is the 35 U.S.C. §371 national stage of PCT ApplicationNo. PCT/IB2012/057761, filed Dec. 27, 2012, which is herein incorporatedby reference in its entirety and which also claims priority to, and thebenefit of, Italian Patent Application No. MI2011A002399, filed Dec. 28,2011, which is herein incorporated by reference in its entirety.

The present invention relates to a multilayer insulation panel forconstruction, in particular an insulation panel having fire-resistantproperties.

Multilayer insulation panels are widely used in building constructions,for example to ensure the thermal insulation of walls, floors and roofs.Such insulation panels for construction of the known type generallycomprise an insulation layer, for example manufactured in polyurethanefoam, sandwiched between two respective backing layers suitable forcladding such insulation layer. Such backing layers perform a dual role:on the one hand they contain the expansion of the polyurethane foam, andon the other give such panels a predefined shape and thickness, at thesame time ensuring dimensional stability.

For example, insulation panels for construction are known wherein thebacking layers of the insulation polyurethane layer are made usingorganic or inorganic materials, such as for example: paper, tarred feltpaper, mono-bituminised fibreglass, mineralised fibreglass, aluminium,multilayer film comprising paper, aluminium and films in plasticmaterial in various combinations.

One example of an insulation panel for construction is described in theEuropean patent application n. 04023033 in the name of the Applicant.

It may be observed that the thickness and composition of the aforesaidbacking layers make such layers flexible, that is such layers can bebent and rolled up.

As known to a person skilled in the art, insulation panels inpolyurethane foam with flexible backing layers of the organic andinorganic type may be classified in five Euro classes depending on afire resistance property shown by each panel when subjected to tests ofvarious types.

Such fire resistance Euro classes are generally indicated by the lettersF, E, D, C, B wherein:

-   -   class E indicates a low level of fire resistance;    -   class B indicates a high level of fire resistance;    -   class F indicates an indeterminate level of fire resistance.

For example, insulation panels in polyurethane with backing layers ofthe metallic type (such as aluminium) of a thickness of more than 80 μmfall into the B class of fire-resistance.

A known test used to evaluate the Euro class of a polyurethane panel isthe UNI EN 11925 method (Kleinbrenner). The duration of such test variesdepending on the classification of the material: 15 seconds for class E,30 for the higher classes. To pass the test, the height of a flamegenerated on the test specimen must be contained below a threshold valueof 150 mm.

A further known test, the SBI test, sets out to estimate thecontribution to the fire of a test specimen subjected to a thermicattack of 40 kW produced by a propane burner for the duration of about20 minutes. In particular such test measures the energy, expressed inkW, generated by the combustion of the test specimen during the test. Ameasure of such energy is obtained indirectly by the consumption ofoxygen registered during the combustion. The energy curve developed as afunction of time is defined the RHR (Rate of Heat Release).

Starting from the aforementioned tests, it is possible to calculate aFIGRA (Fire Growth Rate) parameter with specific algorithms startingfrom the energy curve RHR. In particular, the value of such parameter,measured in Watt/s, makes it possible to discriminate which of theaforementioned Euro classes the insulation panel in polyurethane belongsto.

For example, panels for which FIGRA values of over 750 watt/s arecalculated belong to class E. For FIGRA values between 750 watt/s and250 Watt/s the panels belong to class D. For FIGRA values between 250watt/s and 120 Watt/s the panels belong to class C. For FIGRA valuesbelow 120 watt/s the panels belong to class B.

It is to be observed that for such insulation panels for construction inpolyurethane foam, the performance in terms of fire resistance depends:

-   -   on the type of backing layers used (of the organic or inorganic        type);        -   on the type of polyurethane foam.

For example, the panels which have lower performance (class F) are thosewhich use paper (tarred paper, felt paper, etc.) backing layers. Suchpanels are suitable for applications where there is no risk of directcontact with the flames in the initial stages of the fire (insulation offloors under screeds or perimetral interspaces).

Generally, for a polyurethane insulation panel to be classifiedfire-resistance B or C according to the standard EN 13501-11925/2backing layers of the insulation layer of the metallic type need to beused (such as aluminium sheets having a thickness of more than 80 μm).

The purpose of the present invention is to excogitate and make availablea multilayer insulation panel for construction which offers analternative to the insulation panels using metallic backing layers whilesubstantially maintaining the same properties in terms offire-resistance.

Such purpose is achieved by a multilayer insulation panel forconstruction according to claim 1.

Preferred embodiments of such multilayer panel are described in thedependent claims 2-20.

The present invention also relates to a method of manufacturing themultilayer panel for construction according to claim 21.

The present invention also relates to a method of manufacturing abacking layer of the multilayer panel for construction according toclaim 24 and a relative backing layer according to claim 28.

Further characteristics and advantages of the insulation panel accordingto the invention will be evident from the description given below of itspreferred embodiments, made by way of a non-limiting example withreference to the appended FIG. 1 which shows a transversal cross-sectionview of an example of the multilayer insulation panel for constructionaccording to the invention.

With reference to the aforesaid FIG. 1, a multilayer panel forconstruction having thermal insulation properties according to theinvention is globally denoted by reference numeral 100. Such insulationpanel for construction 100 will also be indicated below as insulationpanel or simply panel.

The insulation panel 100 of the present invention may advantageously beused in the building sector to clad walls, floors and roofs.

Such insulation panel 100 comprises a main layer 1 in insulationmaterial, for example in polyurethane foam. Such main layer 1 comprisesa first surface 10 and a second surface 20 opposite each other.

The insulation panel 100 further comprises a first backing layer 2 ofthe main layer 1 in polyurethane connected to the main layer 1 along theaforesaid first surface 10. In addition, the panel 100 comprises asecond backing layer 5 of the main layer connected to the main layer 1along the second surface 20. In other words, the main layer 1 issandwiched between the first 2 and second 5 backing layers.

At least one of the aforesaid first 2 and second 5 backing layerscomprises a reinforcement layer 3 in fibrous material. Suchreinforcement layer 3 is manufactured, for example, in fibre glass orhybrid fibreglass (e.g. containing from 40% to 60% of polyethyleneterephthalate or PET) or by means of mixed natural, mineral and/orsynthetic fibres. In addition, such reinforcement layer 3 may undergoflame retardant treatments.

It is to be observed that the reinforcement layer 3 is suitable forconferring mechanical resistance and dimensional stability on the panel100.

Advantageously, the at least one of such first 2 and second 5 backinglayers of the panel 100 which comprises the reinforcement layer 3 infibrous material, further comprises a fire-resistant and thermalinsulation layer 4. In the example in FIG. 1, the first backing layer 2comprises both the layer in fibrous material 3 and such fire-resistantlayer 4.

In a preferred embodiment, such fire-resistant layer 4 is manufacturedin an expansive material. In an even more preferred embodiment, suchfire-resistant layer 4 is manufactured in expansive graphite.

It is to be observed that such expansive graphite layer 4 contains, forexample, from 50 g/m2 to 500 g/m2 of graphite. Preferably, such layer 4contains 100 g/m² of graphite.

In addition, such layer in expansive graphite 4 includes graphite inflakes having a mean diameter in the range of 50 μm-2 mm.

Such expansive graphite, if subjected to temperatures to the order ofabout 200° C. begins to expand reaching a maximum expansion if placed incontact with the flames, that is, at temperatures of about 600-1000° C.It is to be observed that, in the presence of flames, the graphite mayincrease its volume by about 50 to about 400 times. In particular thelayer of expansive graphite 4 included in the first backing layer 2 ofthe panel 100, in the presence of flames, is suitable for expanding tocreate a barrier layer which keeps the flames away from the main layer 1in polyurethane or, at least, slows down the advance thereof towardssuch inner insulation layer of the panel 100.

With reference to FIG. 1, in one embodiment of the panel forconstruction 100 according to the invention, the first backing layer 2comprises, in addition, a cladding layer 6 of the reinforcement layer 3configured to be sandwiched between the fire-resistant layer 4 and saidreinforcement layer.

In particular, such cladding layer 6 is manufactured with a mixturecomprising a resin, additives, fillers and a pigment.

It is to be observed that such mixture is suitable for being spread influid form on a surface of the reinforcement layer 3 in fibreglass so asto cover it substantially evenly.

Advantageously, such mixture is suitable for containing the polyurethanefoam in the expansion phase in that it closes partially or completelythe pores present in the structure of the reinforcement layer 3 infibreglass.

Moreover, advantageously, the mixture may comprise a flame retardant andrefractory agent, such as kaolin, which offers a high resistance to thehigh temperatures.

In addition, the mixture may comprises an expanding agent, such asmodified ammonium phosphate which, in the presence of fire, reactschemically releasing a carbon foam having insulating properties to thusretard the raising of the temperature and the contact of the flame withthe main layer 1 in polyurethane.

In one embodiment, the resin of the mixture is an SBR (Styrene ButadieneRubber), acrylic styrol or acrylic polymer type resin.

Moreover, the aforementioned additives of the mixture comprise, forexample, a de-aerating agent, a thickener, an anti-sedimenting agent,wetting agent, an anti-mould agent, anti-bacteria agent, anti-insectagent.

In addition, the fillers of the mixture comprise inert mineral fillers,such as calcium carbonate. The aforesaid mineral fillers may alsocomprise fire-resistant fillers such as for example,colemanite/magnesium hydroxide or another equivalent additive.

It is to be observed that the cladding layer 6 comprised in the firstbacking layer 2 contains from 50 g/m2 to 500 g/m2 of the mixture.

Moreover, the resin of the mixture has a percentage in weight comprisedbetween 5% and 20%. The pigment of the mixture has a percentage inweight of 5% or less. The additives of the mixture have a percentage inweight comprised between 10% and 30%. The inert mineral fillers of themixture have a percentage in weight comprised between 30% and 60%. Thefire-resistant mineral fillers of the mixture have a percentage inweight comprised between 1% and 15%.

The aforementioned expanding agent has a percentage in weight comprisedbetween 1% and 10%. The refractory agent of the mixture has a percentagein weight comprised between 3% and 10%.

With reference to FIG. 1, the first backing layer 2 of the panel 100comprises, moreover, a binding layer 7 positioned on a respectivesurface 8 of the fire-resistant layer 4 in such a way that thefire-resistant layer 4 is sandwiched between the cladding layer 6 andthe aforesaid binding layer 7.

In particular, the binding layer 7 is manufactured by means of aspray-applied aqueous solution of sodium silicates on the respectivesurface 8 of the fire-resistant layer 4, that is to say, on theexpansive graphite. Such sodium silicate solution is suitable forbinding and fixing the flakes of expansive graphite avoiding itsdispersion.

The main characteristics of sodium silicate solutions or equivalentbinding agents which may be used in making the panel for construction100 of the invention are:

-   -   properties of adhesion and rendering inert, thanks to the        ability to give rise to siloxane polymer chains (composed, that        is to say, of alternate atoms of silicon and oxygen) with the        single unit of sodium silicate;    -   binding action by means of physical and chemical adhesion;    -   film-forming action, due to the evaporation of the water, to the        siloxane polymerisation and the increase in viscosity;    -   fire-resistant action, due to the formation of refractory and        thermal insulation films which prevent the close contact of        combustible (wood, paper, cotton etc.) and the combustion agent        (air) essential for combustion;    -   heat resistance, due to the organic nature and above all the        non-volatility of the polymerised silicates.

It is to be observed that, the second backing layer 5 of the panel 100may comprise the same stratigraphy as the first backing layer 2, that isto say the panel 100 has fire-resistant properties on both sides.Alternatively, the second backing layer 5 may be made, for example, inpaper, tarred felt paper, mono-bituminised fibreglass, mineralisedfibreglass, aluminium, multilayer film comprising paper, aluminium andfilms in plastic material in various combinations or in other metallicmaterials.

In a second embodiment, the first backing layer 2 of the panel 100comprises the reinforcement layer 3 in fibrous material and the claddinglayer 6 of such reinforcement layer analogous to those described above.The fire-resistant layer 4, placed over the cladding layer 6, is madefrom a further mixture comprising an expansive material, such asexpansive graphite having the characteristics described above, a resinand additives.

In one embodiment, the further mixture of the fire-resistant layer 4comprises:

-   -   a resin in a percentage comprised between about 40% and 55%;    -   expansive graphite in a percentage comprised between about 35%        and 50%;    -   additives in a percentage of about 10%.

In particular such additives comprise:

-   -   water in a percentage comprised between about 4% and 9.4%;    -   an anti-foaming agent in a percentage comprised between about        0.2% and 2%;    -   a dispersing plasticising retardant agent in a percentage        comprised between about 0.2% and 2%.

In particular, the aforesaid resin is a polymeric dispersion of polymersor copolymers such as, for example, acrylics, vinyls, silicone, silanes,polyurethanes, to which further flame retardant additives are added ifnecessary.

Moreover, the resin is configured to englobe the expansive graphite, inparticular creating a film which binds such graphite to the support 2.In other words, the resin is suitable for plasticising the fireresistant layer 4, at the same time providing a contribution to the fireresistance of said backing layer 2 by means of the further flameretardant additive contained therein.

An example of the method of manufacturing a multilayer panel forconstruction 100 according to the present invention will be describedbelow.

In an initial step of the method, manufacturing of the first backinglayer 2 is envisaged.

Starting from a reinforcement layer in fibrous material 3, such methodcomprises a step of making the cladding layer 6 on the reinforcementlayer 3. In greater detail, such step envisages a step of spreading themineral mixture in fluid form on the reinforcement layer 3 infibreglass.

In a second step, the manufacturing method of the panel 100 envisages astep of forming a fire-resistant layer 4 which comprises a step ofdepositing the expansive graphite in flakes on the still wet claddinglayer 6, for example by means of a “talcing” device of the known type.In particular, during such step at least partial adhesion between theaforesaid fire-resistant 4 and cladding 6 layers takes place and thegraphite is distributed in a substantially even manner.

It is to be observed that the graphite deposited in excess on thecladding layer 6 is removed by making the reinforcement layer 3 beingprocessed run over suitable rollers which make said layer follow a routewith sharp bends to overturn at least twice in succession suchreinforcement layer 3. This way, the graphite deposited in excess ismore likely to fall off by gravity, such step being followed by anaspiration step of such excess graphite.

A third step of manufacturing envisages a step of spraying the sodiumsilicate solution on the graphite layer 4 to make the binding layer 7.

In particular such sodium silicate solution performs a fixing andbinding action of the flakes of graphite of the fire-resistant layer 4,which thus remain adherent to the cladding layer 6 of mineral mixture.

As highlighted above, the aforementioned superposed reinforcement 3,cladding 6, fire-resistant 4 and binding 7 layers form the firstfire-resistant backing layer 2 of the panel 100 in FIG. 1.

In a subsequent fourth step of the manufacturing method of the panel100, a drying step of the first backing layer 2 obtained is envisaged,for example in a hot air furnace, for example at a temperature of about150° C. to 200° C.

Such drying step makes it possible to dry the mineral mixture and fixthe sodium silicate.

It is to be observed that the production line of the backing layer 2works continuously with a roll to roll system wherein the reinforcementlayer in fibre glass is unwound, the various materials deposited and thebacking layer 2 obtained rewound once dry.

The manufacturing method of the panel 100 comprises a step of applyingsaid first backing layer to at least one of the first 10 or second 20surfaces of the main layer 1 in thermally insulating material of thepanel 100.

In a first embodiment, in the case of panels in polyurethane foam, suchapplication step comprises a further step of spraying a polyurethanefoam between the first backing layer 2 as made above and the secondbacking layer 5 which is the same as the first layer 2 or differenttherefrom. In this second case, the second backing layer 5 may be, forexample in tarred felt paper, bituminised glass veil, mineralised glassveil, multilayer film, metal. Such first 2 and second 5 backing layersare suitable for containing the expansion of the polyurethane foam whichforms the main insulation layer 1.

In a second embodiment, such application step comprises a step of gluingsaid first backing layer 2 to at least one of the first 10 or second 20surfaces of the preformed main insulation layer 1. In such latter case,the pre-formed insulation layer may be in polyurethane or alternativelyan insulation layer made with synthetic insulation materials, such asfor example polystyrene foam or extruded polystyrene, phenolic foam,mineral or natural, such as for example the wood fibre which improvesthe performance of reaction to fire of the panel 100.

A further embodiment of the manufacturing method of the first flexiblebacking layer 2 of the panel 100 wherein the fire-resistant layer 4 ismade by means of a further mixture comprising the expansive graphite andplasticising resin is described below.

In particular, starting from a reinforcement layer in fibrous material3, such method comprises a step of making the cladding layer 6 on thereinforcement layer 3. In greater detail, such step envisages a step ofspreading the mineral mixture in fluid form on the reinforcement layer 3in fiberglass.

In a second step, the fire-resistant layer 4 is made by spreading on thecladding layer 6 the further fluid mixture comprising the expansivegraphite, the resin and the additives (water, anti-foam agent,dispersing agent).

Subsequently to such spreading steps, the method comprises a dryingstep, for example in a hot air furnace, of the first backing layer 2. Itis to be observed that the temperature in such furnace is kept below190° C. to prevent accidental expansions of the graphite. Such dryingstep permits both the drying of the mineral compound of the claddinglayer 6 and the drying and plasticising of the resin of thefire-resistant layer 4.

In this second embodiment, the production line of the first backinglayer 2 works continuously with a roll to roll system wherein thereinforcement layer 3 in fiberglass is unwound, the mixtures are spreadand the backing layer 2 rewound once dry. Compared to the manufacturingmethod described in relation to the first embodiment, it is notnecessary to overturn the first backing layer 2 to eliminate the excessgraphite.

The multilayer insulation panel 100 for construction described abovepresents numerous advantages.

Mainly, such panel 100 gives high performance in terms of fireresistance.

In particular, the first backing layer 2 is suitable for conferringfire-resistant properties to the panel 100, in particular if suchbacking layer 2 is applied to both the opposite surfaces 10 and 20 ofthe main insulation panel 1. In fact, the first backing layer 2 protectsthe main layer 1 in polyurethane foam, preventing or slowing down thedirect contact of such foam with the flames.

Such fire-resistant properties are due to the use of expansive graphitein the fire-resistant layer 4. Such graphite, expanding as thetemperature increases, acts as a first barrier to the flames.

In addition, the mixture which forms the cladding layer 6 may also haveflame retardant and refractory agents added to it which offer a highresistance to the high temperatures and pose resistance to the fire. Inother words, the cladding layer 6 represents a second barrier to theadvance of the flames towards the main layer 1 of the panel 100.

Moreover, the mixture of the cladding layer 6 may also comprise phenolicresins to further increase the fire resistance of the panel 100.

It is to be observed that subjecting the panel 100 to a reaction to firetest SBI, the Applicant has calculated experimentally a FIGRA value ofabout 119. Consequently, such panel 100 may be classified in class Baccording to the standard EN 13501-11925/2.

Moreover, the use of sodium silicates in the binding layer 7 furtherincreases the fire resistant properties and heat resistance of the panel100.

Moreover, advantageously, when two or more construction panels 100according to the invention are placed adjacent to each other, the use ofexpansive graphite in the fire resistant layer 4 also permits, in thecase of fire, the protection of the junctions between such adjacentpanels. In fact, the expansion of the graphite as the temperatureincreases makes it possible to seal such junctions.

A person skilled in the art may make modifications and adaptations tothe embodiments of the multilayer insulation panel for construction andrelative manufacturing method thereof described above, replacingelements with others functionally equivalent, so as to satisfycontingent requirements while remaining within the sphere of protectionof the following claims. Each of the features described as belonging toa possible embodiment may be realised independently of the otherembodiments described.

1. Multilayer thermal insulation panel for construction, comprising: amain layer in thermally insulating material comprising a first surfaceand an opposite second surface; a first backing layer of said main layerconnected to the main layer along said first surface; a second backinglayer of said main layer connected to the main layer along said secondsurface; at least one of said first and second backing layerscomprising: a reinforcement layer in fibrous material, a fire-resistantand thermally insulating layer, a cladding layer of said reinforcementlayer configured to be sandwiched between said fire-resistant layer andsaid reinforcement layer, a binding layer positioned on a surface of thefire-resistant layer in such a way that said fire-resistant layer issandwiched between the cladding layer and the binding layer,characterised in that said binding layer is manufactured by means of aspray-applied aqueous solution of sodium silicates on said surface ofthe fire-resistant layer.
 2. Multilayer thermal insulation panel forconstruction according to claim 1, wherein said fire-resistant layer ismanufactured in an expansive material.
 3. Multilayer thermal insulationpanel for construction according to claim 2, wherein said fire-resistantlayer is manufactured in an expansive graphite.
 4. Multilayer thermalinsulation panel for construction according to claim 3, wherein saidlayer of expansive graphite contains from 50 g/m2 to 500 g/m2,preferably 100 g/m2, of graphite.
 5. Multilayer thermal insulation panelfor construction according to claim 3, wherein said layer in expansivegraphite includes graphite in flakes having a mean diameter comprised inthe range 50 m−2 mm.
 6. Multilayer thermal insulation panel forconstruction according to claim 1, wherein said cladding layer ismanufactured with a mixture comprising a resin, additives, fillers and apigment.
 7. Multilayer thermal insulation panel for constructionaccording to claim 6, wherein said resin is a SBR, acrylic styrol oracrylic type polymer resin.
 8. Multilayer thermal insulation panel forconstruction according to claim 6, wherein said additives comprise ade-aerating agent, a thickener, an anti-sedimenting agent, a wettingagent, an anti-mould agent, anti-bacteria agent, anti-insect agent. 9.Multilayer thermal insulation panel for construction according to claim6, wherein said mixture further comprises an expanding agent. 10.Multilayer thermal insulation panel for construction according to claim6, wherein said mixture further comprises a refractory agent. 11.Multilayer thermal insulation panel for construction according to claim6, wherein said fillers comprise inert mineral fillers.
 12. Multilayerthermal insulation panel for construction according to claim 11, whereinsaid fillers further comprise fire-resistant mineral fillers. 13.Multilayer thermal insulation panel for construction according to claim6, wherein said cladding layer contains from 50 g/m2 to 500 g/m2 of saidmixture.
 14. Multilayer thermal insulation panel for constructionaccording to claim 6, wherein said resin of the mixture has a percentagein weight comprised between 5% and 20%.
 15. Multilayer thermalinsulation panel for construction according to claim 6, wherein saidpigment of the mixture has a percentage in weight of 5% or less. 16.Multilayer thermal insulation panel for construction according to claim6, wherein said additives of the mixture have a percentage in weightcomprised between 10% and 30%.
 17. Multilayer thermal insulation panelfor construction according to claim 11, wherein said inert mineralfillers of the mixture have a percentage in weight comprised between 30%and 60%.
 18. Multilayer thermal insulation panel for constructionaccording to claim 12, wherein said fire-resistant mineral fillers ofthe mixture have a percentage in weight comprised between 1% and 15%.19. Multilayer thermal insulation panel for construction according toclaim 9, wherein said expanding agent has a percentage in weightcomprised between 1% and 10%.
 20. Multilayer thermal insulation panelfor construction according to claim 10, wherein said refractory agent ofthe mixture has a percentage in weight comprised between 3% and 10%. 21.Manufacturing method of a multilayer thermal insulation panel forconstruction comprising a main layer in thermally insulating materialprovided with a first surface and an opposite second surface, saidmethod comprising the steps of: providing a reinforcement layer infibrous material, spreading a fluid mineral mixture on saidreinforcement layer to form a cladding layer of the reinforcement layer;evenly depositing graphite in flakes on said cladding layer to form afire-resistant layer; spraying a solution of sodium silicate on saidfire-resistant layer to form a binding layer fixing the flakes ofgraphite to said cladding layer; said superposed reinforcement,cladding, fire-resistant and binding layers forming a first backinglayer of the panel, the method comprising, in addition, the furthersteps of: drying said first backing layer; applying said first backinglayer to at least one of said first or second surfaces of said mainlayer in thermally insulating material.
 22. Manufacturing method of apanel for construction according to claim 21, wherein said step ofapplying the first backing layer further comprises a step of spraying apolyurethane foam between the first backing layer and a second backinglayer, said backing layers acting in conjunction to contain theexpansion of the polyurethane foam which forms the main insulationlayer.
 23. Manufacturing method of a panel for construction according toclaim 21, wherein said step of applying the backing layer comprises astep of gluing the first backing layer to at least one of said first) orsecond surfaces of said main layer in preformed insulating material. 24.Manufacturing method of a backing layer of a multilayer thermalinsulation panel for construction comprising the steps of: providing areinforcement layer in fibrous material, spreading a first fluid mineralmixture on said reinforcement layer to form a cladding layer of thereinforcement layer; forming a fire-resistant layer comprising expansivegraphite on said cladding layer; drying said backing layer. 25.Manufacturing method of a backing layer according to claim 24, whereinsaid step of forming a fire-resistant layer comprises the steps of:spreading a second mixture on said cladding layer, said second mixturecomprising the expansive graphite, a resin and additives. 26.Manufacturing method of a backing layer according to claim 25, whereinsaid second mixture of the fire-resistant layer comprises: a resin in apercentage comprised between about 40% and 55%; expansive graphite in apercentage comprised between about 35% and 50%; water in a percentagecomprised between about 4% and 9.4%; an anti-foaming agent in apercentage comprised between about 0.2% and 2%; a dispersingplasticising retardant agent in a percentage comprised between about0.2% and 2%.
 27. Manufacturing method of a backing layer according toclaim 24, wherein said step of forming a fire-resistant layer comprisesthe steps of: evenly depositing graphite in flakes on said claddinglayer to form the fire-resistant layer; spraying a solution of sodiumsilicate on said fire-resistant layer to form a binding layer fixing theflakes of graphite to said cladding layer.
 28. Backing layer of amultilayer thermal insulation panel for construction, comprising: areinforcement layer in fibrous material, a cladding layer of thereinforcement layer manufactured by spreading a first fluid mineralmixture on said reinforcement layer; a fire-resistant layer comprisingexpansive graphite placed on said cladding layer.
 29. Backing layer of apanel for construction according to claim 28, wherein saidfire-resistant layer is manufactured by spreading a second mixture onsaid cladding layer, said second mixture comprising: a resin in apercentage comprised between about 40% and 55%; expansive graphite in apercentage comprised between about 35% and 50%; water in a percentagecomprised between about 4% and 9.4%; an anti-foaming agent in apercentage comprised between about 0.2% and 2%; a dispersingplasticising retardant agent in a percentage comprised between about0.2% and 2%.
 30. Backing layer of a multilayer thermal insulation panelfor construction, comprising: a reinforcement layer in fibrous material;a cladding layer made on the reinforcement layer; a fire-resistant layerplaced on said cladding layer and comprising expansive graphite. 31.Backing layer of a multilayer thermal insulation panel for constructionaccording to claim 1, wherein said fire-resistant layer is made from afirst mixture comprising the expansive graphite, a resin and additives.32. Backing layer of a multilayer thermal insulation panel forconstruction according to claim 2, wherein said resin is a plasticisingresin configured to englobe the expansive graphite and forms a filmwhich binds the graphite to the backing layer.
 33. Backing layer of amultilayer thermal insulation panel for construction according to claim1, wherein said reinforcement layer is in fibreglass and said claddinglayer is made by spreading a second mineral mixture in fluid form on thereinforcement layer.